Project 6: Sex Differences in Health and Suvival in Strepsirrhine Primates This project will elucidate potential mechanisms underlying the paradox that human males face a survival disadvantage throughout life, despite a seemingly better state of health, especially at old ages. Taking advantage of some of the unique characteristics of Strepsirrhine primates, severalevolution-based hypotheses will be evaluated. The first researchaim is to quantifythe survival consequences of 'risky male behaviors' by dissecting annual survival into time periods when the behaviors of interest occur. Sex-specific survival estimates for wild populations of Microcebus murinus and Cheirogaleus medius will be obtained by statistical modeling of capture-mark-recapture data. In aim 2, the hypothesis will be tested that whereas males outperform females in (physical) functioning, females retain higher immunocompetence. To evaluate this idea, sex-specificage trajectories of functioning and immunocompetence will be constructed for several elements of these two health components using animals from a large captive colony of M. murinus. Additionally, sex differences in health status and causes of death will be analyzed for severalStrepsirrhine species in a retrospective study using the medical histories database of the Duke Lemur Center. In the third aim we will assess the sex differences in seasonal patterns of health over age by comparing indicators of health during the reproductive (high steroid levels) and non-reproductive (low steroid levels) season. To this end, sex-/season-specific immunocompetence and concomitant steroid levels will be measured in captive M. murinus, and sex-/season-specific parasite loads in two wild populations will be quantified. In aim 4 we will test the hypothesis that (due to a more active immune system)females have higher levels of free radical production, but also higher antioxidant defenses comparedto males. In a longitudinal study we will monitor levels of.oxidative stress (reactive oxygen metabolites and antioxidant levels) and oxidative protein damage during aging in both sexes of M. murinus. RELEVANCE (See instructions): The proposed research will advance the development of Strepsirrhine primates, especially the gray mouse lemur (M. murinus) as a non-human primate model of aging, and also extend its domain to address questions on gender-specific health and aging. Ultimately, understanding some of the proximatefactors behind sex differences in survival and health will help to addressgender-specific health issues more efficiently and to predict sex-differentials in survival and health in a given context.